Taper-thread-cutting tool.



Patented July 7, 19M.

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B. BORDEN. TAPER THREAD CUTTING TOOL.

APPLICATION YILED 00123, 1907.

1% f M macs BRADFORD BURDEN, 0h" WARREN, OHIO, ASSIGNOR, BY .tlQQ-ETSIEGZlEtTMENTS, TO THE HART MANUFACTURING COMPANY, 01? CLEVELAND, (EH10), A CORPORATION OF GHIO.

aromas.

To all whom it may concern..- Be it known that I, Bsaorono BORDEN of Warren,in the county of Trumbull an State of Ohio, have invented certain new and useful Improvements in Taper-Thread- Cutting Tools; and I do hereby declare the following to be a full, clear, and exact description of the invention, such as will en-.

able others skilled in the art to which it appertains to make and use the same.

The primary object of this invention is to dispense with the use of leader screws in that class of pipe threading tools wherein a taper thread is-cut by the gradual recession of the chasers.

Heretofore it has been necessary in tools of this class to employ leader screws to initiate the cutting of the chaser teeth into the pipe, or other object to be threaded, and cause the stock to gradually travel toward the work holder. The use of leader screws is attended with no little annoyance .the presence of chips, grit, and other foreign substances greatly interfering with the op.- eration and frequently causing serious inju to the thread, necessitating the substitution of a new leader. Furthermore, when the engagement of the chasers with the pipe is dependent upon the leader screw working in the thread of the work holder, there is a constant friction exerted on the leader screw which necessarily shortens the life of the tool, or at least of the leader screw and its cooperating thread in the work holder. Then again, it has been necessary heretofore to reverse the direction of rotation of the stock to back it ofi from the work, and thechawrs in traversing the thread on the pipe are subjected to considerable wear by contacting with chips etc., which fall into the pipe thread.

I am enabled to dispense with the use of leader screws in taper thread cutting tools, by forming the chasers with short, shallow threads which initiate a screwing engagement between the chasers and the pipe. The short, shallow threads are of gradually increased lengths, that is, the length of each of these threads is greater than that of the thread which precedes it in actingon the pipe so as to thereby easily and gradually bring about the engagement between the cutting threads of the chasers and the pipe. Once this engagement is started the cutting threads follow and continue the hold on the Specification of Letters Patent.

"threads and the pipe.

TAIPER-THREAD-CUTTTNG TOO-L.

Patented July 't, 1914.

Application time October 2a, 1907. Serial Ito. eeaaia initially acting threads are finer than the cutting threads, but this is immaterial. It

is essential, however, that the initially-acting threads-be short and shallow or mutilated, so to speak, that is, that they ;be so formed as to be incapable of acting on the pipe to any greater extent than to bring about the engagement between the cutting For this purpose a line connecting the oints of the short threads lies at an ang e to the axis of the tool greater than a line connecting the points of the cutting threads. By dispensing withthe leader screw the capacit of the tool is greatly augmented. Since t e pitch of the thread to be cut depends solely upon the pitch of the cutting threads of the chasers, different sets of chasers may be used interchangeably. Furthermore, the tool may be on center.

is a'plan view of a threading toolinzconnec tion with which my improvements are employed. Fig. 2 is a side view, partly in sec tion. Fig. 3 is an'enlarged end View, and

Fig. 4 an enlarged side view of one of the chasers. Fig. 5 is a view in pers ective.

Each of the chasers l is forme in its cutting tace with the usual cutting threads 2, which are tapered, as customary. Prefen ably it employ three cuttin threads, but this is not material, the num er being largely controlled by the pitch of the thread to be out. The cutting face of each chaser, from a point adjacent the innermost cutting thread 2, is cut-away or-rounded on the arc of a circle, as shown in Fig. 3, and in this rounded portion 1 form a series of-short,

shallow threads 3, of graduated lengths each thread extending a distance less than the full width of the face of a chaser. That'is to say, these threads at one end terminate flush with the face of a chaser, and are so groundoti or rounded that they present blunt edges, so to speak. Each thread is slightly longer ll than the thread which precedes it in engaging the pipe to be threaded. They have the .necessary spiral formation to msure the proper cooperative work. In starting up the threading operation, these short shallow threads take into the metal of the pipe just suflicient to bring the cutting threads 2 of the several chasers into operative cutting engagement with such pipe. Once this is accomplished, the initially acting threads 3 have no oflice to perform, the cuttin threads 2 alone controlling the travel of t e stock.

In consequence, the tubular sleeve 4 has a perfectl smooth exterior and may be moved longitu inally relative to the work holder 5 by a sliding movement. Heretofore this tubular sleeve has been exteriorl threaded so as to work in a corresponding female thread within the work holder, and consti-- tuted the lead screw.

The chasers recede as the cutting operation progresses so that a taper thread is cut on the pipe. The means shown in the drawings for effecting the gradual outward moveing that the guide posts 6, which are mount-- ment of the chasers corresponds generally with that shown in in Patent No. 862,876, and need notbe here escribed beyond stated on the work holder and are rotated by the turning of the stock, efiect the axial turning of plate 7v with which the chasers engage.

' me advantages of my invention will be apparent. It will be seen that the cost and several annoyance of the leading screw are avoided;

that the range of the tool is increased, bein limited only by the differences in the pitc of the several-sets ofchasers; and that the manipulation of the tool is reatl facili- 4: tated byreason of the fact t at t e stock may be quickly returned to its starting point. Furthermore, the friction which exists in a stock employin a leader screw is'entirely avoided, since t ere is no pull in opposition to that exerted by the chasers on the object being threaded.

In order that one tool may be used to cut both right and left hand threads, by merely changing the chasers, the slots for the latter are exactly on center, as shown in Fig. 1.

I'claim asmy invention: 1. As an article of manufacture, a chaser die for a screw-cuttingdevice,\sa1d die beportion of one taper and another portion, constituting the throat of the die, of another and more abrupt taper, a series of regular cutting threads being cut on such main. portion of the die-face and a series of short, shallow threads for initially gripping the stock being cut on such moreabru tly tapered portion of the die-face, such astnamed threads being of graduated lengths. 3. As an article of manufacture, a chaser 'die for a screw-cutting device, said die being formed with a cutting face having a main portion of-one taper and another portion, constituting the throat of the die, of another and more abrupt taper, a series of regular cutting threads being eaten such main portion of the die-face and a series of short, shallow threads forinitially gripping the stock'being out on such more abruptly tapered tportion of the die-face, such lastnamed t made being of graduated lengths and each such thread extending a distance less than the full widthof the die-face.

' 4. As an article of manufacture, a chaser die for a screw-cutting device, said die being formed with a cutting face having a main portion of one taper and another portion, constituting the throat of the die, rounded off on another and more abrupt taper, a series of regular cutting threads being-cut on suchmain portion of the dieface and a series of short, shallow threadsfor initialliy ripping the stock being cut on such roun e portion of the die-face.

5. As an-article of manufacture, a chaser die for a screwrcutting' device,-said die being formed with a cutting face. having a 7 main portion of one taperand another portion, constituting the throat of the die, rounded off on the arcof a circle so as to be of another and more abrupt taper, a series of regular cutting threads eing cut on such main portion of the die-face and a series of short, shallow threads for initiall gripping initially gri ping the stock being cut on such more a ruptly tapered portion of the die-face; of a member movably supporting said dies; and means ada ted positively to retract said dies during t e cutting operation, the length of the more abruptly tapered portion of the respectiveie-faces eing so correlated with the rate of retraction of said dies that the threads on such portion, after serving to initially grip the stock, are relieved from forming the threads threads for initially ing cut on such roun dies that the threadsof such portion,

on the stock and the burden of this operation thrown on the threads on the less abrupt portion of thedie-face.

7. In a screw-cutting device, the combination with chaser dies, each formed with a single cutting face having a main portion of one taper and another ortion, constituting the throat of the die, rounded oil on the arc of a circle so as to be of another and more abru t taper, a series of regular cutting threa 5 being cut on such main portion of the die-face and a series of short, shallow ripping the stock beed portion of the dieface; of a member movably supporting said dies; and means adapted posltively to retract said dies during the cutting operation, the length of the more abruptly tapered portion of the res ective die-faces being so cor:

e rate of retraction of said after grip the stock, are rethe threads on the related with t serving to initially lieved from formin stock and the bur en of this operation thrown on the threads on the less abrupt portion of the die-face.

8. In a taper thread cutting tool, in combination, a work holder, a stock having a smooth tubular portion movable in said work holder, a series of chasers mounted in said stock, and means for causing the chasers to recede as the cutting operation progresses, such chasers havingeach a series of regular cuttin threads and a seriesof short shallow threa s of graduated lengths for initiating the engagement between the chasers and the object to be threaded, a line connecting the points of the short threads lying at an angle to the axis of the tool greater than a line connecting the points of the cutting threads.

In testimony whereof, I have slgned this specification in the presence of two subscribing witnesses. v

BRADFORD BURDEN.

Witnesses FRANCIS S. MAGUIRE, JOHN A. MURPHY. 

